Soil can become compacted or sod-bound with the passage of time and consequently does not absorb moisture as well as desired. Also, compacted soil does not enable air to penetrate into the soil.
Various types of apparatus have been previously proposed for use in aerating soil. However, such apparatus has exhibited various disadvantages and drawbacks which have limited the effectiveness of such apparatus.
For example, U.S. Pat. No. 2,778,291 describes a rotary renovator which includes a drum having teeth mounted on its periphery. A box for distributing fertilizer is carried on the frame behind the drum, and a chain driven by a gear on each end of the drum causes fertilizer to be distributed as the apparatus is towed. The teeth are mounted to the periphery of the drum in fixed locations. Consequently, the spacing between adjacent rows of teeth is fixed and cannot be changed. For use in certain types of soil, this is a significant disadvantage.
U.S. Pat. No. 767,890 describes a rotary harrow in which rows of diamond-pointed teeth or shovels are mounted on the surface of a drum. The apparatus is said to be useful for breaking up clods in a plowed field. The type of teeth or shovels as shown in the patent would not be suitable for aerating compacted soils, however.
U.S. Pat. No. 2,509,463 describes a land clearing machine for removing small stumps and roots from beneath the top soil. Curved teeth on a drum penetrate into the ground to engage stumps or roots and pull them out of the ground. Stripper teeth are positioned near the rear of the apparatus for removing roots or other items pulled from the ground by the teeth on the drum. This device would not be satisfactory for aerating ground because it would tend to disrupt or damage roots of growing grass, for example.
U.S. Pat. No. 3,084,747 also describes apparatus for clearing roots, etc. from the ground. The apparatus includes a driven drum canted obliquely from the forward direction of travel of the drum, and the drum is driven in a direction opposite to forward direction of travel. Curved blades on the drum are driven into the ground to engage roots, etc. and drag them to the surface. Such apparatus would not be suitable for aerating soil because it would be too disruptive of growing grass and plants.
U.S. Pat. No. 1,696,654 describes a roller cultivator for use in orchards. The apparatus includes one or more heavy rollers with spade-like or chisel teeth or blades which cut through ground cover and dig up the soil as the device is towed between rows of trees. The apparatus is intended to dig up the ground and not merely puncture it. Accordingly, such apparatus is not suitable for aerating.
U.S. Pat. No. 2,857,835 describes apparatus for fracturing soil. Teeth are mounted on the surface of a drum. The teeth holders include a V-shaped web having triangular wings and a slotted tip. Points are frictionally held to the tips of the holders. No lateral adjustment or movement of teeth or teeth holders is possible.
U.S. Pat. No. 3,528,508 describes sod disturbing and replanting apparatus. The apparatus includes teeth on a drum for extending into the ground. A box on the rear of the apparatus distributes grass seed or the like. There is no provision for adjusting the lateral spacing between teeth on the drum.
U.S. Pat. No. 4,821,811 describes a towable support frame for a pair of 12-row implements in side-by-side relation. There is no description of field aerating apparatus.
There has not heretofore been described aerating apparatus which enables lateral adjustment of teeth on a rotating drum.